A typical hypodermic syringe includes a syringe barrel with a mounting collar for threadedly engaging the hub of a needle assembly. A needle assembly includes a hub and a needle cannula which are connected. In cases where the needle assembly is maintained separately from the syringe until shortly prior to use, the medical practitioner selects an appropriate needle assembly for the procedure being carried out. The needle assembly is removed from its sterile package, and the hub of the needle assembly is threadedly engaged with the mounting collar of the syringe barrel.
Liquid pharmaceuticals and other injectable liquids are often stored in rigid containers which can be accessed using a hypodermic syringe. Some containers for injectable liquids are glass vials with elastomeric closures that can be penetrated by the needle on a hypodermic syringe. To access the liquid in a vial, the plunger of the hypodermic syringe is moved in a proximal direction to draw into the syringe barrel a volume of air substantially equal to the volume of medication that is desired. The sharp distal end of the needle is then urged through the elastomeric closure of the vial, and the air in the syringe barrel is injected into the vial. The distal end of the needle and the vial engaged therewith are then pointed gravitationally upwardly. The practitioner ensures that the distal tip of the needle is covered by the medication in the vial by manipulating the needle and the vial with respect to each other. The plunger of the hypodermic syringe is then moved proximally to draw the desired volume of medication through the needle and into the chamber of the syringe barrel.
After withdrawing a desired volume of medication from a vial, the medical practitioner may inject the medication into either a patient, another vial or an injection site of an intravenous set or catheter. There is a trend toward needleless I.V. systems which do not require a pointed needle cannula to pierce the injection site of an I.V. set. There are systems that have injection sites covered by a pre-slit septum which can be accessed by a blunt cannula. Accordingly, after withdrawing medication from a vial using a sharp needle the user must remove the needle and install a blunt cannula if the medication will be used with an I.V. set having a pre-slit septum.
At the time of prefilling the syringe it may not be known whether medication will be injected through an injection site having a pre-slit septum, which requires a blunt cannula, or through an injection site having a pierceable elastomeric septum which requires a needle assembly having a cannula sharp enough to pierce the septum. In this latter case the practitioner may use the hypodermic needle assembly which was used to fill the syringe.
There is a need for a single device which will allow filling of a syringe from a vial having a pierceable stopper and the subsequent delivery of the medication to an I.V. set through a blunt cannula. There is also a need for a single device which can be used for withdrawing medication from a vial having a pierceable stopper and for injecting this medication through an injection site having a pierceable septum or a pre-slit septum.